Why does everyone expect free photos?

I’m not a professional by any means but I do have a good eye for photography. I focus mainly on landscape and nature because I don’t really want to go out of my way to set up a photo shoot. My little brother is graduating this year and he needs senior photos. My dad assumed I’d take them without asking and now ima tuck in an awkward position. I don’t do that kind of work and I’m not good at it. He knows what type of photography I do but doesn’t really care because he doesn’t want to hire someone. Not only that but I do most of my work on my phone because, again, I’m not a professional. I don’t even know what to do at this point. I’d love to help them out but I feel like it’s going to end so badly.